The controlled fabrication of two and three-dimensionally ordered structures is important for the nanoengineering of materials and devices, where “nano” is loosely defined as small, typically in the range of microns or smaller. In particular, metal nanostructures are increasingly important building blocks for new materials due to their shape-dependent plasmon response and thus their tunable optical properties. The emergent field of plasmonics is particularly concerned with how surface plasmons propagate, localize, or interact on metal nano- and microstructures. Exploitation of surface plasmon propagation in these regimes can be used to develop new devices in nano-optics and optical computing, waveguides, biomolecular and chemical sensor arrays, optical filters, and surface enhanced Raman substrates (SERS).
Microcontact printing, a form of soft lithography, is a nonphotolithographic technique in which molecular patterns are transferred to surfaces using a polydimethylsiloxane (PDMS) stamp. The polymer stamp is molded from a master template, which is the relief of the desired printed pattern, and is wetted by a solution of the molecule to be transferred. This technique is fast, simple, and inexpensive and has inspired several new fabrication methods. For example, planar metal structures have been fabricated using microcontact printing wherein a pattern of protective alkanethiols is stamped onto a metal surface and chemical etching is used to remove the non-stamped regions. A second method uses a PDMS stamp to transfer palladium colloid directly to a surface onto which copper is deposited by electroless plating. Still, another method includes functionalizing a surface with molecules that attach to metal colloid. In the aforementioned method described, selective deposition of Pt and Pd can be accomplished using hexafluoroacetylacetonate complexes and Metalorganic Chemical Vapor Deposition (MOCVD).
While a number of methods exist for producing planar metal structures employing microcontact printing, methods for producing a wide variety of geometrically distinct two dimensional (2-D) arrays of metal patterns without lithographically defining a different 2-D master template for each new pattern and without the need for chemical etching are not known to exist. Hence, it is desirable to produce planar metal structures according to this desirable new method.